As wireless devices have become more compact and wireless technology improves, many such devices now have more than one wireless circuit on them. For example, many cell phones can now connect to a local network, such as a Bluetooth network or a Wi-Fi network, in addition to their basic wireless telephone connection. Unfortunately, this can lead to signal interference in some situations.
For example, if one wireless circuit on a cell phone is transmitting a signal at the same time as another wireless circuit on the cell phone is receiving a signal, the transmitting signal may interfere with the receiving signal because of the near-far problem. In such a situation, the transmitting signal will be relatively more powerful than the received signal, and may overwhelm the received signal to such a degree that the received signal cannot be properly detected.
This is a particular problem when the two wireless circuits operate in close or adjacent frequency bands. For example, one wireless circuit on a single mobile device might operate on a band used by the International Mobile Telecommunications Advanced wireless communication standard, also called the 4G Long Term Evolution (4G LTE) standard, while another wireless circuit on that same mobile device might operate on a band in the industrial, scientific, and medical (ISM) radio bands. For example, the 4G LTE standard can transmit between 2300 MHz and 2400 MHz, while certain wireless LAN devices, such as Bluetooth and IEEE 802.11/Wi-Fi, can employ adjacent ISM bands (between 2402-2472 MHz).
In particular, an unacceptable level of interference may occur when a 4G LTE circuit on a mobile device is transmitting (i.e., uplinking) an uplink signal, while a Bluetooth/Wi-Fi circuit on the same mobile device is simultaneously attempting to receive (i.e., downlink) a downlink signal. In such a circumstance, the 4G LTE uplink signal could be of sufficient power that the RF filters in the Bluetooth/Wi-Fi receiver would be capable of providing sufficient RF isolation to allow the Bluetooth/Wi-Fi receiver to properly receive the Bluetooth/Wi-Fi downlink signal while the 4G LTE uplink signal was being transmitted.
In such a case, the only current solution to this issue is time domain coexistence between the technologies based on signaling between the controllers of the two networks (e.g., between a 4G LTE base station and a Bluetooth/Wi-Fi controller). In other words, the two network controllers must provide information that allows a mobile device to ensure that the transmission and reception of potentially interfering circuits does not occur.
Existing solutions for time domain coexistence typically rely on a real-time indication of the device uplink/downlink status. For example, a 4G LTE base station provides a real-time indication of a device uplink/downlink status (i.e., whether it will be transmitting or receiving signals) according to a 1 ms resolution window. Current devices require Bluetooth/Wi-Fi circuits to only transmit Bluetooth/Wi-Fi signals when the 4G LTE circuit is not transmitting 4G LTE signals, and to terminate such transmitting Bluetooth/Wi-Fi signals whenever this real-time indicator may indicate that the a coexisting 4G LTE circuit might transmit again. This allows the Bluetooth/Wi-Fi circuit a maximum airtime of 1 ms before its next decision point.
This is a particular issue in cases in which the Bluetooth/Wi-Fi circuit requires some sort of acknowledgment of its transmission. In such a case, sufficient time must be allowed for the receipt of the acknowledgment signal before an adjacent 4G LTE circuit begins to transmit. This is because even though the Bluetooth/Wi-Fi circuit could successfully transmit at the same time that a co-located 4G LTE circuit was simultaneously transmitting, the Bluetooth/Wi-Fi circuit could not successfully receive an acknowledgment at the same time that the co-located 4G LTE circuit was transmitting.
As a result, conventional designs only allow Bluetooth/Wi-Fi circuits an opportunity to transmit for 1 ms at a time, allowing sufficient time for an acknowledgment to be received before the next 1 ms window begins. This can significantly limit the throughput of the Bluetooth/Wi-Fi circuit, since it is constantly interrupted every 1 ms to stop transmitting and to monitor the real-time transmission status of the 4G LTE circuit.
Furthermore, this is true even if the 4G LTE circuit does not have any data to transmit in a given resolution window. The Bluetooth/Wi-Fi circuit must nevertheless stop transmitting and wait until the real-time indicator indicates that the current resolution window is free of transmissions before beginning to transmit again.
It would be desirable, therefore to provide an optimized scheme that increases Bluetooth/Wi-Fi throughput by allowing the usage of airtime in increments greater than 1 ms. Such a scheme would allow a Bluetooth/Wi-Fi circuit to transmit its data were quickly, and thus allow it to enter a sleep or low-power state earlier, thereby saving battery power for the device.